Filter Press Function:

The Water and Wastewater Equipment Company Filter Press is a liquids/solids filtration and separation device.  Filtration is the process of separating the suspended solids from a mixture of liquids and solids, called slurry.  The slurry is directed towards the filter cloth, as the liquid passes through, the filter cloth catches the solids.

The Water and Wastewater Equipment Company filter press is easy to understand, easy to operate, and most importantly, yields the highest dry solids content from your filtered slurry or cake.  With less liquid content in your cakes, your hauling and disposal costs will be lower and your product yields higher.

The filter press is made up of two principle components.  They are the filter pack and the skeleton or press frame.  This is true for all filter presses of the “plate and frame, recessed plate or diaphragm plate” design and encompasses press frames of both the sidebar and overhead plate suspension types.

The filter press skeleton has one chief function, which is to hold the filter pack together against the pressures developed internally during the filtration process.  The terms used to describe the filter press skeleton may vary slightly from manufacturer to manufacturer, but the sub-components remain essentially the same.  The components of the filter press include the stationary head, follower head, closure end and sidebars.  Depending on the ancillary equipment supplied, a filter press skeleton may have some additional function such as plate shifting for cake discharge, automatic cake release, or cloth washing (etc.).

The filter press skeleton provides for the influent and effluent connections with the filter pack.  These are the piping connections, which pass through the stationary head and connect the feed and discharge manifold to the filter pack.

The filter pack is where the actual liquid/solid separation process takes place.  The pack consists of a series of alternating filter elements that, when held together in the filter press skeleton, form a series of chambers.  Each chamber wall known as the drain-field has a series of raised cylinders or grooves, which is then covered with a porous cloth medium.  These grooves or “pips” form a flow path for the liquid draining from the press.  At alternating corners of the drain-field, interconnecting holes join the drain-field to the four corner discharge ports.  When the plates are held together in a plate pack, the corner discharge eyes form individual manifolds connecting the drain-fields of the plates with the external piping of the filter press.  The center feed inlet port also forms a manifold that connects with the individual cake collection chambers of the plate pack

In operation, a solids laden slurry is pumped under pressure into the filter press chambers through the piping at the stationary head of the filter press, via the feed connection.  As each cake chamber fills with slurry, the liquid passes through the cloth medium, across the drain-field, through the drain ports and exits via gravity out of the corner discharge eyes.

The prime function of the media in cake filtration is to provide a porous support structure for the filter cake as it develops and builds.  Initially, some solids may pass through the cloth media causing a slight turbidity in the filtrate, but gradually the larger particles within the slurry begin to bridge the openings in the media reducing the effective opening size.  This allows smaller particles to bridge these reduced openings initiating the cake filtration process.  Once a layer of solid particles achieves 1-1/2 to 2mm in thickness, this layer serves as a pre-coat to separate out finer and finer particles as the cake builds in thickness, yielding a filtrate which is very low in turbidity.

The driving force behind the slurry (typically 100 psi) is provided by an air operated double diaphragm transfer pump.  With a gravity drain on the filtrate side of the filter press, a pressure differential between the feed pressure and the gravity discharge is created across the media and the filter cake solids as they build in thickness.  It is the existence of this pressure differential, not just the feed pump pressure, which causes the filtering action to occur.  Solids within the slurry will flow to the area of the cake development with the lowest pressure differential, resulting in a filter cake that builds uniformly over the drain-field on either side of the chamber walls.  This process is the basis for cake filtration.

This solids deposition process continues until the filter cakes forming on the individual chamber walls bridge at the center, completely filling the filter press with solids.  It is at this point that the filtration process is complete.

Once this is achieved, the hydraulic closure of the filter press is released and individual filter elements are separated.  The collected solids are discharged, usually by gravity, to an appropriate receptacle.

Water and Wastewater Equipment Company Filter Press Features Chart: